The invention relates to microstrip transmission lines in integrated circuits and methods of making same.
In a conventional microstrip transmission line geometry in an integrated circuit structure, a dielectric layer is formed over a ground plane and spaced metal microstrip lines are formed on the dielectric layer. This conventional transmission line geometry, in which the metal lines stand on the entire dielectric plane, has problems of low characteristic impedance due to fringing fields, low signal propagation velocity due to the reduced "speed of light" in the dielectric, and high wafer stress due to thermal expansion mismatch between the dielectric layer and the metal ground plane.
It is desirable to provide a microstrip transmission line geometry with higher characteristic impedance, lower fringing fields, less capacitive coupling and crosstalk, increased signal propagation velocities, and lower wafer stress than presently available. Such an improved microstrip transmission line geometry would greatly enhance integrated circuit performance.